A heavier arrow with THE SAME DIAMETER is less affected by the wind. If you really believe that a lighter arrow is lossing it's KE at a faster rate you need to study the charts a little bit more. FACT - a smaller diameter shaft is LESS affected by the wind = SURFACE AREA. The small difference in weight DOES NOT offset the larger surface area variable - which is what is considered when thinking about crosswinds!!!!
I don't know where shaft diameter came into this debate, but I didn't assume there was a difference. It's quite easy to shoot a very heavy narrow diameter arrow. I can also shoot a very large diameter light carbon if I choose to.
Why then, would you suggest "rainbowing one in there"????
Hmm, I re-read my post and as I thought, I didn not suggest that anywhere. In fact, I suggested that inside 30 yards, there would be very little trajectory advantage to a light arrow, yet there could be a substantial disadvantage in accuracy - especially out of his particular bow set-up.
but you really should take a look at the math involved and then sink some carbons next to your fat alluminums out of the same setup.
Where are you getting this "fat aluminums"? I don't shoot aluminum. Besides, if I did, such a test is meaningless in my eyes. Targets don't have moving, lubricated muscle and hard bone to deflect the arrow. It is my contention that penetration in a live animal is dependent on very different factors than a static, man made target. In addition, accuracy is far more important in my view.
My recomendation is still, pay no attention to speed. Look carefully at the factors that cause a broadhead to fly well, and take whatever speed results.